Infection with human immunodeficiency virus type 1 (HIV-1) is typically characterized by a progressive disintegration of the immune system, acquired immune deficiency syndrome (AIDS), and death. However, some individuals infected HIV-1 virus do not develop disabled immune systems or AIDS. Because a cure or vaccine for AIDS has eluded researchers for years, these individuals and the virus they harbor may provide essential clues toward the development of vaccines or treatments against HIV.
Some of these asymptomatic HIV-1 infected individuals have variant strains that affected the virus' ability to grow. Viral gene mutations were causing the HIV-1 to grow at a relatively slow rate (growth attenuation). The resultant low levels of virus created a non-lethal, asymptomatic infection (Iversen (1995) J. of Virology 69:5743-5753; Hua (1996) Virology 222:423-429).
Differences between the deadly form of the virus and the non-lethal variants were found in portions of the viral genome able to regulate how fast the virus and grows and multiplies. This creates an exciting new way to design an effective vaccine against HIV-1. Slow-growing, non-lethal (attenuated) viral mutants can be designed as vaccines to protect against AIDS. Thus, there exists a great need for new ways to attenuate retroviruses, such as HIV-1. The present invention fulfills this and other needs.